I'm sorry but this is not helpful at all lol.
Where you able to figure this out?
Yeah, you just set it up on the site. Google "anidb API setup" and you should be able to figure it out.
How can you use projects already created and hosted by AniDB? There are plenty of projects already created here: https://anidb.net/software I want to just download one of these, connect it to Bazarr, and things should work. I can't find a tutorial anywhere :(
You're thinking of two different things.
An API is a way for software to say "I want to see info about this" and the website will send that. To do this, you set up access with a unique identifier that is specific to you/the app.
The software you linked is stuff people have built. It uses the API to function, but you can't piggyback off of that. Think of it this way - the API is Facebook, and each piece of software has its own login. If you wanted a Facebook login, you would have to make your own - downloading a piece of software doesn't mean you'd suddenly be able to use their login, right?
Try the instructions here - it's for something else, but the part where you create your API access is the same. Start under where it says, "To get a Client Name and Client Version please follow the following steps." and when you're done you'll have exactly what you need for Bazarr.